The present invention concerns the field of surgery and in particular the field of autologous bone harvesting for reconstructing bone defects. Preferably, but not exclusively, the invention applies to the field of oral surgery.
After a dental element has been lost (due to trauma or pathology) the alveolar ridge generally undergoes restructuring that always ends up with a reduction of its original volume. Such a reduction very often determines the lack of adequate bone structure for the correct three-dimensional insertion of a dental implant. There are various reconstruction techniques of atrophic alveolar ridges. The material considered “gold standard” for such surgery is autologous bone, i.e. harvesting of a bone element from the patient himself so that it can be autografted in the atrophic area.
The body of the mandible has an outer face, an inner face, a lower margin or base and a rear face. The outer face has the chin symphysis in the middle, which is the midpoint of the join of the two separate primitive outlines of the bone and ends at the bottom with the mental protuberance. In this same face it is possible to see, at the level of the 2nd premolar tooth, the lateral mental foramen, the opening of the channel of the mandible; at the level of the 2nd and 3rd molar tooth there is an oblique ridge, the buccinator groove, on which the homonymous is located. The upper end of the buccinator groove marks the boundary between body and ramus. The side lip of the groove becomes more substantial and represents the outer oblique line of the mandible.
The locations generally preferred for intra-oral harvesting are the outer oblique line and the mental symphysis. The limits and the risks of such a procedure are described in the literature and include:                risk of lesion of the lower alveolar nerve;        risk of lesion of the mental nerve close to the homonymous foramen;        risk of lesion of the dental neuro-vascular tissue;        risk of mandible fracture;        risk of lesion of the dental roots;        volumetric limit with regard to the bone defect to be treated, i.e. limit to the amount and size of bone that it is possible to harvest.        
Such risks are determined by the fact that it is impossible to clinically translate the detailed information obtained from radiograph examinations, TAC or other that allow a three-dimensional reconstruction of the anatomy of the patient. In other words, it is very complex, even if a detailed analysis of the anatomy of the patient has been carried out through three-dimensional imaging techniques, to make what has been analysed in the three-dimensional reconstructions of the anatomy correspond with the actual arrangement of the anatomical structure of the patient “live” due to the lack of real reference points between the visible external anatomical structure and the inner one.
In the anatomical area of the external oblique line, the risk areas are:
rear limit to the anatomical boundary with the area of the mandibular ramus where it is extremely complex to determine “with the naked eye” the profile and the depth of the alveolar channel (lower alveolar nerve);
medial or internal limit where it is extremely complex to determine “with the naked eye” the profile of the roots of the teeth present and/or of the lingual bone theca;
front limit where it is extremely complex to determine “with the naked eye” the profile of the alveolar nerve close to the mental foramen;
more generally, it is extremely complex to determine “with the naked eye” an accurate control of the work axis of the bone cutting tools, be they rotary or piezoelectric tools.
In the area of the mental symphysis the risk areas are:
lower limit where it is extremely complex to precisely determine “with the naked eye” the lower edge of the mandible (presence of the mental muscle whose uppermost attachment must be respected);
upper limit where it is extremely complex to determine “with the naked eye” the profile of the roots of the front teeth;
rear limit where it is extremely complex to determine “with the naked eye” the profile of the loop of the lower alveolar nerve and of that of the incisor;
more generally, also in this case it is extremely complex to determine “with the naked eye” an accurate control of the work axis of the bone cutting tools, be they rotary or piezoelectric tools.
The fact that it is not possible to work with accuracy and certainty means an approximation in performing the surgical procedure, reduction of the bone volumes harvested and increased risks of the surgery.